Detergents used in industrial and institutional warewashing machines have been problematical, whether liquid, powder or solid detergents are used. These problems include: safety problems in handling the detergents, particularly high alkaline (more than 12% caustic) detergents; chemical stability; caking; softening; dehydration; homogeneity; and dispensing equal amounts of detergent and additives at a uniform rate. There are also manufacturing problems with the institutional and industrial detergents. Most of these problems have been adequately discussed in prior art. See Re. 32,763 and 32,818, and the references cited therein, for a discussion of such problems.
In order for a detergent to be effective, whether of high or low alkalinity, the detergent must be able to clean all surfaces, be dispensed uniformly and be used with minimal foaming. To meet these requirements, additives are combined with the detergent. Chlorine-based compounds and defoamers are the common additives used in these detergents. The chlorine-based compounds are particularly important for removing coffee and tea stains.
For industrial and institutional ware washing machines, the detergents used should have the characteristics of being dispensed from a container or the like uniformly, that is, at a controlled rate, into the wash water. Highly alkaline detergents are the most suitable for superior cleaning. In addition to the uniform dispensing of the detergent, the components of the detergent itself should be homogeneous such that there is no variation in the strength of the detergent delivered including any additives within the detergent. This homogeneity can be easily achieved with liquid detergents but for high alkaline solid detergents homogeneity has been difficult to achieve.
Prior to the liquid cast solid detergents disclosed in the above-referenced reissue patents, the problems of solid detergents were acknowledged to be the difficulty in forming solid detergents with high alkalinity which would provide a constant rate of delivery, in blending highly alkaline detergents with sequestering agents, and in mixing highly caustic materials in an aqueous solution to produce a homogeneous product. The other additives typically found in the detergents, such as chlorine-based compounds and defoamers, if added during the formation of the liquid cast solid detergents, could either react with the components, separate within the casting mass, and/or lose their efficacy. According to the disclosures of the reissue patents, the then prior art problems of the difficulty of safely forming a solid homogeneous detergent were overcome by forming an aqueous solution of an alkaline hydratable component and a hardness sequestering agent and then casting the liquid which, upon cooling, formed a hard solid product. Although the compositions disclosed in these patents overcame some of the prior art problems, the process for making such a liquid cast detergent is relatively time consuming.
As described in the reissue patents, a liquid composition is made under very carefully controlled conditions and the liquid composition cast into a receptacle. However, the liquid composition has to be continuously agitated and the temperature controlled up to the time when the liquid composition is cast. Although this process then represented an advance in the state of the art, the forming of the liquid composition further required careful control because of the mixing of the reactive components. Lastly, certain additives, such as surfactants and defoamers, could not simply be blended into the final liquid detergent composition mix in a uniform, dispersed manner.
The present invention is directed to a process which overcomes the problems of forming and casting liquid detergent compositions of non-compatible materials and to the product of the process. The inventive process and product eliminate the need to segregate within the solid detergent certain additives, such as surfactants and defoamers. The product of the invention has uniformly dispersed therethrough the major components of the detergent as well as the other additives. The detergent and additives are dispersed at a uniform rate.
With the process disclosed herein, a cake-like high-alkaline detergent is provided with less water content than other available solid detergents. This results in a cake-like detergent which therefore can deliver more cleaning power per unit weight.
Applicant's invention provides a solid cake-like detergent, which is homogeneous. Applicant's invention forms the homogeneous solid cake-like detergent by blending the components of the detergent as powders to form a dry detergent mixture, then flowing the dry powder mixture through a water spray, moistening the particulates, which then fall into a vibrating receptacle where the moistened powder detergent mix forms into a solid cake.
As used in this disclosure, the term flowing powder means that the particulates of the powdered detergent mixture can easily move and change their relative position within the mixture without separation from the stream such that there is intimate contact between the moisture and the particulates substantially throughout the flowing powder stream of particulates. That is, the particulates of the detergent mixture are distributed at a rate and in an amount such that the particulates flow in the flowing powder stream without being carried out of the system. Under this condition, the use of particulates tends to equalize the composition of the reaction mixture and temperature throughout the moving powder stream. This uniformity of mixing and temperature dispersion has successfully overcome the prior art problems of forming homogeneous high alkaline solid detergents.